1. Field of the Invention
The present invention relates to a semiconductor device, which uses a through plug for connection between substrates, and a method of manufacturing the same.
2. Description of the Related Art
Recently, multi-chip semiconductor devices have attracted special interest. Multi-chip semiconductor devices can improve the performance of the entire devices, using several chips. A chip direct-laminated type multi-chip semiconductor device has been proposed as one of the above multi-chip semiconductor devices. In this kind of multi-chip semiconductor device, several chips are electrically connected to each other using a plug (chip through plug) penetrating through a chip.
In order to form the chip through plug, first, a metal plug 82 is buried and formed in the surface of a Si substrate (Si wafer) 81 (see FIG. 12A). The back surface of the Si substrate 81 is previously ground by mechanical polishing with the use of a grinding wheel having a high grinding speed directly before the metal plug 82 is exposed (see FIG. 12B). Thereafter, the Si substrate 81 is thinned by wet or dry etching or CMP (Chemical Mechanical Polishing) until the metal plug 82 projects from the back surface of the substrate by several μm (see FIG. 12C).
Actually, before the metal plug 82 is buried and formed, a trench inner wall in which the metal plug 82 is buried is coated with a dielectric film, etc. Here, the dielectric film, etc are omitted for simplification of the explanation.
In the back surface grinding process by the grinding wheel shown in FIG. 12B, a grinding tape 83 is stuck onto the Si substrate 81, as illustrated in FIG. 13. In a state where a grinding table 84 is placed on the grinding tape 83, the back surface of the Si substrate 81 is ground.
In order to monitor the back surface thickness (amount) ground by the grinding wheel, the total thickness of the Si substrate 81 and the grinding tape 83 is measured using a contact type thickness monitor.
However, non-uniformity (e.g., ±10 μm) occurs in the thickness of the grinding tape 83; for this reason, non-uniformity also occurs place in the thickness of the back surface ground by the grinding wheel.